Such apparatus is known in various embodiments. These prior art apparatus have either front axle steering or rear axle steering. In both cases the area covered by the rear cleaning means does not coincide with that of the front cleaning means if the apparatus makes a turn, for example around obstacles. This makes it necessary to move back and forth in such areas in order to complete the cleaning operation. As an alternative, the rear cleaning means can be made wider than the front cleaning means so as to obtain complete coverage by the rear cleaning means. However, this increases the total width of the apparatus making it more difficult to handle, especially in areas with obstacles which may interfere with the protruding rear cleaning means.
The object of the present invention is to remove this problem in an effective way. To obtain the object, the invention provides an apparatus according to claim 1.